The researcher who discovered that the UK government's phone encryption standard has a huge backdoor installed has made another discovery: GCHQ's rejection of a better encryption standard because it didn't allow for undetectable spying.
Dr Steven Murdoch has updated his original post on the MIKEY-SAKKE standard, developed by UK listening post GCHQ, to include a document from the 3GPP standardization group that was responsible for the 3G mobile phone standard and which also developed the 4G and LTE standards (i.e., what your phone currently uses).
That document [PDF] stems from a meeting back in 2010 and outlines how a representative from the National Technical Assistance Centre (NTAC) – GCHQ's decryption and data analysis arm – worked to reject the MIKEY-IBAKE standard because it could produce a slight delay in people's phone calls when they were being intercepted.
"Due to the timing and interaction required to perform the man-in-the-middle attack during call setup, there will be additional latency in call setup," it reads. "This will be especially pronounced when large numbers of surveillance subjects are active in one region or one switch."
It goes on to note that the IBAKE standard would mean if an individual's connection was tapped, it could interfere with other authentication efforts, i.e., someone might notice they were under surveillance. And it noted that the standard would make it difficult to go back retroactively and listen to past conversations.
Although the document is not new – it was published on the whistleblower Cryptome website back in 2014 – its relevance has only just come to light thanks to the UK government's efforts to push the MIKEY-SAKKE standard for the latest end-to-end phone encryption products.
That effort is not limited to government departments: it is also being marketed to the broader commercial world through a product spec it has called Secure Chorus by highlighting its "government-grade security." It has also set itself up as an evaluator of other products, one example being Cryptify Call, available for iOS and Android.
MIKEY-SAKKE is mentioned possibly for the first time in the 2010 rejection of the IBAKE approach. The document notes: "In light of these requirements, UK government has developed a similar scheme, MIKEY-SAKKE, which supports 3GPP SA3 LI requirements and has additional benefits such as low latency."
That standard that the UK government specifically developed to allow for full and unnoticeable surveillance is the same one that six years later it is now trying to push into the expanding commercial market for more secure phone calls. It is notable that it makes no mention of the ability to invisibly intercept calls in its description of the protocol.
In short: the security services are trying to get people to hardwire the same standards that make it possible to intercept existing phone calls into products that are specifically designed to avoid that exact scenario.
Well, you can't blame them for trying. ®